Right coronary autoregulation in conscious, chronically instrumented dogs

Archer

2014

Circulation Research

379

163

The right ventricle (RV) is the major determinant of functional state and prognosis in pulmonary arterial hypertension (PAH). RV hypertrophy (RVH) triggered by pressure overload is initially compensatory but often leads to RV failure. Despite similar RV afterload and mass some patients develop adaptive RVH (concentric with retained RV function), whilst others develop maladaptive RVH, characterized by dilatation, fibrosis and RV failure. The differentiation of adaptive versus maladaptive RVH is imprecise but adaptive RVH is associated with better functional capacity and survival. At the molecular level, maladaptive RVH displays greater impairment of angiogenesis, adrenergic signaling and metabolism than adaptive RVH and these derangements often involve the left ventricle. Clinically, maladaptive RVH is characterized by increased NT-proBNP levels, troponin release, elevated catecholamine levels, RV dilatation and late gadolinium-enhancement on magnetic resonance imaging, increased 18fluorodeoxyglucose uptake on positron emission tomography and QTc prolongation on the electrocardiogram. In maladaptive RVH there is reduced inotrope responsiveness due to G-protein receptor kinase (GRK2)-mediated downregulation, desensitization and uncoupling of β-adrenoreceptors. RV ischemia may result from capillary rarefaction and/or decreased right coronary artery perfusion pressure. Maladaptive RVH shares metabolic abnormalities with cancer including aerobic glycolysis (resulting from a FOXO1-mediated transcriptional upregulation of pyruvate dehydrogenase kinase, PDK), and glutaminolysis (reflecting ischemia-induced cMyc activation). Augmentation of glucose oxidation is beneficial in experimental RVH and can be achieved by inhibition of PDK, fatty acid oxidation, or glutaminolysis. Therapeutic targets in RV failure include chamber-specific abnormalities of metabolism, angiogenesis, adrenergic signaling and phosphodiesterase-5 expression. The ability to restore RV function in experimental models challenges the dogma that RV failure is irreversible without regression of pulmonary vascular disease.

Section: Right Ventricular Ischemiamentioning

confidence: 98%

The Right Ventricle in Pulmonary Arterial Hypertension

Archer

2014

Circulation Research

379

163

“…Right ventricular ischemia may reflect reduced right coronary artery perfusion pressure. However, right ventricular function is usually preserved as long as coronary perfusion pressure, the difference in pressure between the aorta and the right ventricle in systole or diastole, exceeds 50 mm Hg 221. In PAH, systemic (aortic) hypotension and a rise in right ventricular pressure (in both systole and diastole) combine to reduce the pressure gradient that drives perfusion of the right coronary artery, contributing to right ventricular ischemia.…”

Section: Pathogenesis Of Pahmentioning

confidence: 99%

Pulmonary arterial hypertension: pathogenesis and clinical management

Thenappan

Ormiston

et al. 2018

BMJ

660

608

Pulmonary hypertension is defined as a resting mean pulmonary artery pressure of 25 mm Hg or above. This review deals with pulmonary arterial hypertension (PAH), a type of pulmonary hypertension that primarily affects the pulmonary vasculature. In PAH, the pulmonary vasculature is dynamically obstructed by vasoconstriction, structurally obstructed by adverse vascular remodeling, and pathologically non-compliant as a result of vascular fibrosis and stiffening. Many cell types are abnormal in PAH, including vascular cells (endothelial cells, smooth muscle cells, and fibroblasts) and inflammatory cells. Progress has been made in identifying the causes of PAH and approving new drug therapies. A cancer-like increase in cell proliferation and resistance to apoptosis reflects acquired abnormalities of mitochondrial metabolism and dynamics. Mutations in the type II bone morphogenetic protein receptor (BMPR2) gene dramatically increase the risk of developing heritable PAH. Epigenetic dysregulation of DNA methylation, histone acetylation, and microRNAs also contributes to disease pathogenesis. Aberrant bone morphogenetic protein signaling and epigenetic dysregulation in PAH promote cell proliferation in part through induction of a Warburg mitochondrial-metabolic state of uncoupled glycolysis. Complex changes in cytokines (interleukins and tumor necrosis factor), cellular immunity (T lymphocytes, natural killer cells, macrophages), and autoantibodies suggest that PAH is, in part, an autoimmune, inflammatory disease. Obstructive pulmonary vascular remodeling in PAH increases right ventricular afterload causing right ventricular hypertrophy. In some patients, maladaptive changes in the right ventricle, including ischemia and fibrosis, reduce right ventricular function and cause right ventricular failure. Patients with PAH have dyspnea, reduced exercise capacity, exertional syncope, and premature death from right ventricular failure. PAH targeted therapies (prostaglandins, phosphodiesterase-5 inhibitors, endothelin receptor antagonists, and soluble guanylate cyclase stimulators), used alone or in combination, improve functional capacity and hemodynamics and reduce hospital admissions. However, these vasodilators do not target key features of PAH pathogenesis and have not been shown to reduce mortality, which remains about 50% at five years. This review summarizes the epidemiology, pathogenesis, diagnosis, and treatment of PAH.

“…diastolic perfusion pressure) may also be reduced, thereby impairing RCA flow in diastole 82,83 . When the RCA perfusion pressure falls below 50 mmHg, RV contractile function declines 84 .…”

Section: Adaptive Versus Maladaptive Rvhmentioning

confidence: 99%

Right Ventricular Adaptation and Failure in Pulmonary Arterial Hypertension

Canadian Journal of Cardiology

Huston

Kutty

et al. 2015

155

102

Pulmonary arterial hypertension (PAH) is an obstructive pulmonary vasculopathy, characterized by excess proliferation, apoptosis-resistance, inflammation, fibrosis and vasoconstriction. While PAH therapies target some of these vascular abnormalities (primarily vasoconstriction) most do not directly benefit the right ventricle (RV). This is suboptimal since a patient’s functional state and prognosis are largely determined by the success of the adaptation of the RV to the increased afterload. The RV initially hypertrophies but may ultimately decompensate, becoming dilated, hypokinetic and fibrotic. A number of pathophysiologic abnormalities have been identified in the PAH RV, including: ischemia and hibernation (partially reflecting RV capillary rarefaction), autonomic activation (due to GRK2-mediated down-regulation and desensitization of β-adrenergic receptors), mitochondrial-metabolic abnormalities (notably increased uncoupled glycolysis and glutaminolysis), and fibrosis. Many RV abnormalities are detectable by molecular imaging and may serve as biomarkers. Some molecular pathways, such as those regulating angiogenesis, metabolism and mitochondrial dynamics, are similarly deranged in the RV and pulmonary vasculature, offering the possibility of therapies that treat both the RV and pulmonary circulation. An important paradigm in PAH is that the RV and pulmonary circulation constitute a unified cardiopulmonary unit. Clinical trials of PAH pharmacotherapies should assess both components of the cardiopulmonary unit.